In manufacturing processes and within manufactured capital goods themselves, precise and repeatable motion is useful and often essential. For example, in manufacturing processes ranging from machining to textiles to electronics, tool heads or other items move back and forth and must do so precisely and repeatedly over enormous numbers of cycles. In another example, specimens and instrumentation move relative to each other within laboratory analytic devices to collect data on the samples and must do so precisely and repeatedly.
Guide wheels attached to support bases and riding on rails is one class of guided motion technology providing precise and repeatable kinematics. For example, U.S. Pat. No. 3,661,431 discloses guide wheels and tracks in which guide wheels 1 cooperate with rails 14 such that the guide wheels may move along the rails.
While guide wheel and rail systems are highly precise and reliable conveyances, industry trends require guide wheels that are increasingly compact and low profile, as well as increasingly able to carry larger weights over longer lifetimes. With respect to lifetime and reliability, the economic costs to a manufacturing operation of replacement time or failure can be substantial. For example, on the order of millions of dollars per day of down time in semiconductor wafer manufacturing. In capital goods as well, the cost of replacement time or failure may also be substantial because replacement of guide wheels may collaterally necessitate realignment or recalibration of other components. This is especially the case in optical systems.
One solution to the technical demands of increased lifetime and weight carrying capacity is to simply increase the scale of guide wheels. Proportionally scaling up a guide wheel assembly can increase the load capacity. As well, a larger wheel assembly will have a longer lifetime for a given load because the load-bearing portions operate farther from their maximal capacity and rotating parts rotate less frequently to travel a given distance.
Scaling is, however, not a solution under many circumstances because of a need to maintain wheel size. Often tight spacing or additional replacement costs that would be necessitated by increasing wheel size make scaling the wheels impossible or impractical or uneconomical.
What is needed, therefore, are guide wheel assemblies with increased lifetime and load-carrying capability as compared to present devices, which increases being realized without scaling the wheel size.